000014629 001__ 14629
000014629 037__ $$a6143
000014629 041__ $$aEnglish
000014629 100__ $$aDelgado, J. M.
000014629 100__ $$aApel, H.
000014629 100__ $$aMerz, B.
000014629 245__ $$aFlood trends and variability in the Mekong river
000014629 260__ $$c2010
000014629 260__ $$b
000014629 490__ $$aArticle
000014629 507__ $$aMFOLL
000014629 520__ $$a<span class="pb_abstract">Annual maximum discharge is analysed in the Mekong river in Southeast Asia with regard to trends in average flood and trends in variability during the 20th century. Data from four gauging stations downstream of Vientiane, Laos, were used, covering two distinct hydrological regions within the Mekong basin. These time series span through over 70 years and are the longest daily discharge time series available in the region. The methods used, Mann Kendal test (MK), ordinary least squares with resampling (OLS) and non-stationary generalised extreme value function (NSGEV), are first tested in a Monte Carlo experiment, in order to evaluate their detection power in presence of changing variance in the time series. The time series are generated using the generalized extreme value function with varying scale and location parameter. NSGEV outperforms MK and OLS, both because it resulted in less type II errors, but also because it allows for a more complete description of the trends, allowing to separate trends in average and in variability.<br /> <br /> Results from MK, OLS and NSGEV agreed on trends in average flood behaviour. However, the introduction of a time-varying scale parameter in the NSGEV allowed to isolate flood variability from the trend in average flood and to have a more complete view of the changes. Overall, results showed an increasing likelihood of extreme floods during the last half of the century, although the probability of an average flood decreased during the same period. A period of enhanced variance in the last quarter of the 20th century, estimated with the wavelet power spectrum as a function of time, was identified, which confirmed the results of the NSGEV.<br /> <br /> The authors conclude that the absence of detected positive trends in the hydrological time series was a methodological misconception due to over-simplistic models.<span class="pb_toc_link"><br />
000014629 653__ $$aflood
000014629 653__ $$aLaos
000014629 653__ $$aresearch
000014629 653__ $$arivers
000014629 653__ $$awater
000014629 650__ $$aHazards and disaster
000014629 650__ $$aFloods
000014629 650__ $$aNatural resource management
000014629 650__ $$aWater management
000014629 691__ $$aHazards and disaster
000014629 691__ $$aFloods
000014629 691__ $$aNatural resource management
000014629 691__ $$aWater management
000014629 773__ $$pHydrology and Earth System Sciences, 14, 407-418, 2010
000014629 8564_ $$uhttp://lib.icimod.org/record/14629/files/6143.pdf
000014629 980__ $$aARTICLE